The use of syringes to retain a fluid, such as a medicament, is well known. Devices and methods have also been heretofore suggested and/or utilized to control delivery of medicament from a syringe by controlling the movement of the syringe piston.
It is also known that the piston of a syringe can be driven by an electric motor through a linkage that can include a lead screw arrangement (see, for example, U.S. Pat. Nos. 4,529,401, 4,435,173 and 4,563,175) or a rack and pinion arrangement (see, for example, U.S. Pat. Nos. 3,395,704 and 4,532,460), and it has been suggested that a stepper motor might be utilized to drive a syringe piston (see, for example, U.S. Pat. Nos. 4,435,173 and 4,481,454). In addition, a stepper motor with reduced power consumption has also been heretofore suggested (see, for example, NASA Technical Briefs, Volume 8, Number 4, MFS-25119, Summer 1984), as has use of optical sensors to sense shaft or piston movement (see, for example, U.S. Pat. Mo. 4,475,666).
Prior devices and methods for controlling movement of the syringe piston have, however, not proved to be fully effective, at least for all intended purposes. Such prior known devices and/or methods have, for example, been ineffective in precisely controlling medicament delivery, have lacked the ability to deliver changing amounts of medicament over different time periods, have lacked safeguards against undesired use, have not been fully capable of safe and dependable operation, and/or have lacked simplicity of structure and/or operation.